In the manufacture of an electronic device such as a semiconductor device, a plasma processing, for example, plasma etching is performed on a processing target object. This plasma processing is performed by using a plasma processing apparatus.
The plasma processing apparatus generally includes a chamber main body, a first electrode, a second electrode, a first high frequency power supply, a first matching device, a second high frequency power supply and a second matching device. The chamber main body provides an internal space therein as a chamber. The first electrode and the second electrode are arranged with a space within the chamber provided therebetween. The second electrode is a lower electrode and is embedded in a mounting table configured to mount a processing target object thereon. The first high frequency power supply is configured to generate a first high frequency power for plasma generation. The first high frequency power is supplied to one of the first electrode and the second electrode. The second high frequency power supply is configured to generate a second high frequency power for ion attraction. The second high frequency power is supplied to the second electrode. In the plasma processing apparatus, a variable reactance element of the first matching device is controlled to match an output impedance of the first high frequency power supply and an impedance at a load side thereof. Further, a variable reactance element of the second matching device is controlled to match an output impedance of the second high frequency power supply and an impedance at a load side thereof. In the plasma processing apparatus, a gas supplied into the chamber is dissociated by a high frequency electric field generated between the first electrode and the second electrode, and the processing target object is processed by active species such as ions and/or radicals.
In the plasma processing apparatus, a high frequency power having a modulated level may be supplied from at least one of the first high frequency power supply and the second high frequency power supply. That is, a modulated wave, whose level is modulated such that a level in one of two alternating periods is lower than a level in the other of the two alternating periods, may be used. A technique of using the high frequency power in the plasma processing apparatus is described in Patent Documents 1 to 3 as follows.
Patent Document 1: Japanese Patent Laid-open Publication No. 2009-071292
Patent Document 2: Japanese Patent Laid-open Publication No. 2009-033080
Patent Document 3: Japanese Patent Laid-open Publication No. 2012-009544
In the plasma processing apparatus, various combinations of the first high frequency power output from the first high frequency power supply and the second high frequency power output from the second high frequency power supply may be considered. By way of example, as a first combination, the first high frequency power is a modulated wave, whereas the second high frequency power is a continuous wave. As a second combination, the first high frequency power is a continuous wave while the second high frequency power is a modulated wave. As a third combination, both the first high frequency power and the second high frequency power are modulated waves. In this third combination, modulation frequencies of the first high frequency power and the second high frequency power may be same or different.
As stated above, if multiple combinations of the first high frequency power and the second high frequency power are selectively used in the single plasma processing apparatus, calculation of an impedance for matching operation of each of the first matching device and the second matching device becomes complicated. Accordingly, with respect to the various combinations of the first high frequency power and the second high frequency power, it is required to achieve a relatively simple calculation of the impedance for the matching operation of each of the first matching device and the second matching device.